1. Field of the Invention
The invention relates generally to the field of digital signal modulation and coding. More particularly, the invention relates to a multiple rate codec using convolutional and block coding with a phase shift keying constellation.
2. Description of the Related Art
Presently in transmitting and receiving digital data across noisy channels, it is difficult to find a suitable compromise between adequate bandwidth efficiency and adequate error correction capabilities. With full error correction coding, the bit rate becomes too low or the bandwidth requirements too high. With only modest error correction coding, much of the transmitted signal can become unrecoverable at the receiver. In order to provide a robust communications link, the data should be recoverable and yet bandwidth limitations should be honored. When the quality of the channel changes, a compromise that was optimal only a few seconds ago may become a poor choice.
The present invention allows the transmitted bit rate to be changed as the quality of the channel changes. This provides a better combination of error correction coding for the available channel. It is suitable for any kind of digital communications but is particularly suitable for wireless low mobility digital data communications systems.
A method and apparatus that provide a bandwidth efficient variable bit rate communication of digital signals in a noisy channel is described. According to one aspect of the present invention, the invention includes receiving a puncturing request, puncturing a data packet in accordance with the puncturing request, creating a puncturing code indicating the puncturing that has been applied to the data packet and transmitting the punctured data packet and the puncturing code.